The Analgesic Effects of Different Swing Patterns of Interferential Currents on Cold-induced Pain

Abstract

Despite the widespread use of interferential currents (IFC) by physiotherapists to manage painful conditions, evidence for analgesic effects is sparse, and information on the optimal stimulating parameters is lacking. The aim of this single-blind placebo controlled preliminary study was to examine the analgesic effects of 6∧6 and 11 swing patterns of IFC on cold-induced pain in healthy subjects. Fifteen healthy university student volunteers were randomly allocated to receive either active IFC 6∧6, active IFC 11 or sham IFC. During the experiment, which lasted a total of 60 minutes, each subject completed six identical ten-minute experimental cycles of the cold-induced pain test. During each cycle the time to pain threshold and pain intensity rating measurements were recorded as outcome measures. Experimental cycles 1 and 2 were pre-treatment, cycles 3 and 4 during treatment (active IFC or sham IFC) and cycles 5 and 6 were post-treatment. The main finding of this study was that there was a larger rise in pain threshold for subjects receiving the 6∧6 swing pattern when compared to 11 IFC or sham IFC. The rise in pain threshold was rapid in onset for the 6∧6 IFC group, occurring within ten minutes of IFC switch on and having returned to baseline within 20 minutes of IFC switch-off. No effects were found for pain intensity ratings during treatment. In conclusion, the differential analgesic effects between 6∧6 and 11 swing patterns of IFC found in the present study may have implications for IFC settings used in the clinic. However, one should be cautious in extrapolating the results of this preliminary study on healthy subjects to patients suffering pain from injury and disease. It is imperative to confirm these findings in patient populations. Despite the widespread use of interferential currents (IFC) by physiotherapists to manage painful conditions, evidence for analgesic effects is sparse, and information on the optimal stimulating parameters is lacking. The aim of this single-blind placebo controlled preliminary study was to examine the analgesic effects of 6∧6 and 11 swing patterns of IFC on cold-induced pain in healthy subjects. Fifteen healthy university student volunteers were randomly allocated to receive either active IFC 6∧6, active IFC 11 or sham IFC. During the experiment, which lasted a total of 60 minutes, each subject completed six identical ten-minute experimental cycles of the cold-induced pain test. During each cycle the time to pain threshold and pain intensity rating measurements were recorded as outcome measures. Experimental cycles 1 and 2 were pre-treatment, cycles 3 and 4 during treatment (active IFC or sham IFC) and cycles 5 and 6 were post-treatment. The main finding of this study was that there was a larger rise in pain threshold for subjects receiving the 6∧6 swing pattern when compared to 11 IFC or sham IFC. The rise in pain threshold was rapid in onset for the 6∧6 IFC group, occurring within ten minutes of IFC switch on and having returned to baseline within 20 minutes of IFC switch-off. No effects were found for pain intensity ratings during treatment. In conclusion, the differential analgesic effects between 6∧6 and 11 swing patterns of IFC found in the present study may have implications for IFC settings used in the clinic. However, one should be cautious in extrapolating the results of this preliminary study on healthy subjects to patients suffering pain from injury and disease. It is imperative to confirm these findings in patient populations.